A phase I study of R-(-)-gossypol (AT-101) in combination with cisplatin (P) and etoposide (E) in patients with advanced solid tumors and extensive-stage small cell lung cancer (ES-SCLC)

Abstract

e13502 Background: AT-101 [R-(-)-gossypol acetic acid] (AT) is an orally-administered BH3 mimetic that lowers the threshold for apoptosis by direct binding to Bcl-2, Bcl-xL, Mc1–1, Bcl-W, and through upregulation of the proapoptotic proteins Noxa and Puma. Bcl- 2 is over-expressed in >80% of SCLC. In vitro study using SCLC cells showed that treatment with EP had synergistic cytotoxic effects in suppression of Bcl-2. This is a phase I dose-escalation study of AT in combination with EP with an expanded cohort of patients with ES-SCLC. This study is being conducted to determine the maximum tolerated dose (MTD), pharmacokinetics and activity of AT with EP ± pegfilgrastim (F) in patients with advanced, refractory solid tumors and/or ES-SCLC. Methods: This study used standard eligibility criteria except patients must not have received prior therapy that inhibits the Bcl-2 family. At dose level 1, patients received P 60 mg/m2 on day 1 and E 100 mg/m2 on days 1, 2, and 3 every 21 days. AT was administered 30 mg orally BID on days 1, 2 and 3 of each cycle. Results: 10 patients have been enrolled; 7 men, 3 women. Tumor types: 6 lung; 2 prostate; 1 head & neck; 1 unknown primary. 2 of 5 patients enrolled at dose level 1 experienced a DLT of neutropenic fever in cycle 1. Three subsequent patients were enrolled to dose level -1 (20 mg BID x 3 days, d1–3) which was well tolerated. Additional patients are being enrolled at dose level 1a (EP+AT with F). Grade 3/4 toxicities related to AT without F at dose level 1 and -1 were as follows: ANC (8), leucopenia (7), febrile neutropenia (2), low hemoglobin (1), thrombocytopenia (1), elevated AST (1), cardiac ischemia/MI (1), diarrhea (1). There were no reported grade 3/4 toxicities in two patients at level 1a. Four patients had stable disease; two progressive disease and four patients were unevaluable. Conclusions: The MTD without F was established at AT 20mg orally BID, P 60 mg/m2 on day 1, and E 100 mg/m2 on days 1, 2, and 3 every 21 days. The MTD with F has not yet been established. Accrual continues at dose level 1a. Subjective and objective evidence of clinical activity has been observed in patients with refractory solid tumors. This study was supported by NCI, UO1 CA062491, SAIC 25XS097 and 1ULRR025011. No significant financial relationships to disclose.